Expansible rotary drill bits



A- W. KAMMERER, JR

EXPANSIBLE ROTARY DRILL BITS Oct. 8, 1957 Filed May 26, 1955 2 Sheets-Sheet l IN VEN TOR.

as i? AQCl-IER WKAMME2E.Q,zI2.

1957 A. w. KAMMERER, JR 2,809,016

EXPANSIBLE ROTARY DRILL BITS Filed May 26, 1955 2 Sheets-Sheet 2 age/ 37.6.

III/7 25 ARCHER WKAMMEEEE, ([2.

BY J20 2 ArriezvEK United States Patent Patented Oct. 8, 1957 EXPANSIBLE ROTARY DRILL BITS Archer W. Kammerer, Jr., Fullerton, Califi, assignor of three-fifths to Archer W. Kammerer, and one-fifth to Jean K. Lamphere, Fullerton, Calif.

Application May 26, 1955, Serial N 0. 511,187

Claims. (Cl. 255-76) The present invention relates to rotary drill bits, and more particularly to rotary drill bits of the expansible type adapted to be lowered through well casing, for the purpose of drilling or enlarging a well bore below the casing to a greater diameter than the inside diameter of the casing.

An object of the invention is to provide a rotary drill bit having cutters expandible laterally outward by hydraulic pressure, in which the cutters are releasably retained in their outwardly expanded position in the absence of hydraulic pressure in the drill bit, and despite the lack of drilling weight on the cutters.

Another object of the invention is to provide an expansible rotary drill bit having cutters expanded laterally outwardly by hydraulic pressure, and embodying a detent device for retaining the cutters in their expanded position, in which the detent device can be availed of for relieving the fluid pressure tending to hold the cutters in their expanded position, to insure retraction of the cutters when the bit is to be retrieved from the well bore. Liquids are permitted to pass to and from the hydraulic portions of the drill bit through the detent device, but the detent device is of such character as to prevent solid particles from passing therethrough to the hydraulic portion of the apparatus, thereby minimizing any tendency for such hydraulic portion to become plugged.

A further object of the invention is to provide an expansible rotary drill bit having cutters expanded laterally outward by hydraulic pressure, and embodying a detent device for retaining the cutters in their expanded position or for inadvertently allowing the cutters to be expanded when their retention in a retracted position is desired.

This invention possesses many other advantages, and has other objects which may be made more clearly apparent from a consideration of a form in which it may be embodied. This form is shown in the drawings accompanying and forming part of the present specification. It will now be described in detail, for the purpose of illustrating the general principles of the invention; but it is to be understood that such detailed description is not to be taken in a limiting sense, since the scope of the invention is best defined by the appended claims.

Referring to the drawings:

Figure 1 is a longitudinal section through an embodiment of the invention disposed in a well bore, with the cutters and other parts in their initial and retracted positions; V

Fig. 2 is a longitudinal section similar to Fig. 1, disclosing the cutters locked in their fully expanded position;

Fig. 3 is an enlarged fragmentary longitudinal section disclosing the hydraulic and detent portion of the apparatus in the relative position they occupy when the cutters are in their retracted position;

Fig. 4 is a view similar to Fig. 3, disclosing the relative position of the parts when the cutters are in the eX- panded pos tiQndisclosed in Fig. 2;

Fig. 5 is an enlarged cross-section taken along the line 55 on Fig. 1;

Fig. 6 is an enlarged cross-section taken along the line 66 on Fig. 1;

Fig. 7 is an enlarged cross-section taken along the line 77 on Fig. 1;

Fig. 8 is an enlarged cross-section taken along the line 8-8 on Fig. 2.

As disclosed in the drawings, a rotary expansible drill bit A is provided which can be secured to the lower end of a string of drill pipe B extending to the top of a well bore, by means of which the drill bit is lowered through a string of well casing (not shown) to a region below the casing shoe (not shown) where the hole enlarging operation is to commence. The general type of expansible drill bit shown in the drawings is both illustrated and described in Patent No. 2,545,036, to which attention is invited for certain structural details that are not disclosed nor described herein in detail.

The upper portion of the rotary drill bit consists of a tubular mandrel 10 having an upper pin 11 threadedly connected to the lower end of the string of drill pipe B. This mandrel includes an upper kelly or drill stem member 12 slidably splined to the main body 13 of the bit, as by having a lower, non-circular portion 14 of the kelly adapted to be telescopically received in a companion socket 15 formed in the main bit body.

The mandrel 10 has a limited range of longitudinal movement within the body 13, its downward movement being determined by engagement of the lower end 16 of the kelly with an inwardly directed body shoulder 17, its upward movement being limited by engagement of an external shoulder or piston portion 18 of the kelly, which fits within a counterbore 19 in the body of the tool above its socket portion 15, with a cylinder head 20 secured to the body. This cylinder head 20 constitutes the upper portion of a hydraulic cylinder 21 in which the piston 18 operates, the cylinder head having an upper outwardly directed flange 22 adapted to engage an upwardly facing shoulder 23 in the body to prevent downward movement of the head relative to the body. Upward movement of the head 20 with respect to the body is prevented by one or more split snap retainer rings 24- received within an internal groove 25 in the body and extending across the upper end of the cylinder head.

The upper end of the body 13 is closed by an annular upper guide member 26 including a depending portion 27 received within the upper end of the body and adapted to rest upon or be disposed closely adjacent the retainer rings 24. This upper guide member has an upwardly tapering guide surface 28 in its flange portion 29, which rests on the upper end of the body 13, the guide being removably secured to the body by a split wire snap ring 35), which may be round in cross-section, received within an internal groove 31 in the body and also within an opposed external groove 32 in the guide itself. The ring 3%? may completely fill the internal body groove 31, but when disposed therein only extends partially into the guide groove 32, such groove being of suflicient lateral depth as to permit the wire ring to be disposed com pletely therewithin when the guide 26 is inserted into and removed from the upper portion of the bit body 13.

In assembling the upper guide 26 in the body 13, a longitudinally extending screw 33 having a tapered lower end 34 is threaded downwardly in a companion bore 35 in the guide through use of a suitable screw driver or other tool (not shown), the tapered end 34 of the screw engaging the outer peripheral portion of the split wire ring 30, to retain it completely within the peripheral guide groove 32. The guide 26 can then be inserted into the body to its fullest extent, whereupon the screw 33 is to:

ated... o. le te. t. th n. he. h eaded b re. 3.5. and.

33 can then be threaded downwardly; so; that its; tapered ow an 34 nga e he: nner: n iphe ak por o f h wire ring, to prevent the latter from retracting from, the nnerody r o e- 51:. n he v nt it. is agai es to withdraw the guide 26 from the body 13, the screw 3: ot tediand lev te n: he hr aded; o e 35.. her upona sufficient upward; force exerted; on the guide 26 will,- cause: the curved: Wall of the; internal groove 31; to am. qrfo e h ms. 30 n ar ycomp e ly into the u de roo low h u to b o p y lev t -dz out: o h b y 113; o o

The: o o y 3 a a p ural ty o expansible p t mounted on. it, including; cutter-supporting members 36 pivotallymounted in body slots: 37- on; hinge pins 38 secured-to the body. As specifically illustrated in the drawings, each: hingepin. 38 extends through a bore 39 in a, cuttersupporting member and into body bores 40, 41; on; opposite sides of each body slot. To minimize wear on theparts, each hingepin 38 may operate within a bushing; 42 receivedv within the counterbore 41 in the body on-one side of theslot 37, thisbushingbeing prevented from moving laterally. outward by engaging a body-shoulder 43 which the counterbore provides. Similarly, a bushing 44 is. provided around;the other end portion;of'the pin within the other body bore 40, engaging a; shoulder 45 which prevents the; bushing from moving outwardly ofthe tool body. The, central portion of the hingepin 38 also hasawear bushing 46 mounted thereon which has aworkingfit within the'holeor bore '39 through the cutter supporting member 36.

Qne;end-portion 47 of the hinge pin 38 is reduced in diameter andhas a central portion removed to form a relatively short tubular section that has circumferentially spaced transverse slots, 48 cut through its wall to provide a; plurality of fingers 49-. Opening into the tubular portion is a threaded hole 50 in the pin adapted to receive a screw: 51 which has a tapered head 52, as well as a slot, for;the reception of asuitable screw driver (not shown). The end of the pin; 38 adjacent the tubular portion 47 engages the body shoulder-45, thetubular portiodextending in an outward direction through the body bore adjacent;such; shoulder and projecting into an enlarged bore portion 53 opening to the exterior of the body, the base 4;o f;this enlarged boreportion being tapered or inclined in: an; inward direction toward the body shoulder/l5.

The bushings-42, 44; 46 are inserted in place and the cutter supporting member; 36 disposed in the body slot 3 7,1with its bushing 46 in; alignment with the other bushings'42', 44. The cylindrical pin 38 is then inserted through; one; ofthe transverse bores 41 in the body and through the bushings 42, 46, 44 until its other end portion; engages the body shoulder 45, with the fingers 4's ofjthepin disposed'in the enlarged counterbore 53. The finger s- 49 can then bebent outwardly through use of a suitable; tool, to lie against the tapered shoulder 54. Such engagement of the fingers with the tapered shoulder prevents axial movement of the pin 38 in one direction, whereas engagement of the pin with the other shoulder 45 preyentsits axial movement in the opposite direction.

The-fingers- 49 are prevented from being inadvertently retractedby threading the screw 51 into the threaded bore 50 in the. pin, the tapered head 52 on the screw engaging theoutwardly bent fingers 49 to hold them in such outw-ardiy bent-fashion. To facilitate insertion of the screw 51, the other end of thecyiindrical pin may betprovidedwitha screw driver slot 55 toreceive a screw driverand preventthe pin 38., from rotating during the threading ot the screw into, the threaded bore. Once the scr 51 has been assembled in this manner, it can 4. be prevented from inadvertent loosening by bending one of the fingers 49a back over against the head portion 52 of the screw.

In the event it is desired to withdraw the pin 38 from its assembled position, the finger 49a bent against the head of the screw is forced laterally outward, the screw 51 is removed, and the fingers 49 bent inwardly sufficiently to pass through the small diameter; bore portion surrounded by the shoulders 45, 54, then allowing the pin 38 to be withdrawn fro m the body through the opposite bore portion 41 of, the latter.

Each cutter supportingmember 36 depends from a hinge pin 38 and terminatesin a: bearing supporting pin 60 inclined inwardly and downwardly. A side roller cutter 61 is rotatably mounted on each bearing supporting pin, being mounted on anti-friction roller and ball bearing elements 62, 63 rollable on the bearing supporting pin 60. The ballbearingelements 63 lock the cutters against endwise movement on the bearing. supporting pin 60, as well as transmitting axial and radial thrusts between the cutter andsupportingpin. The roller bearing elements 62 transmit primarily radial thrusts between these parts. The manner of mounting the ball and roller bearing elements 62, 63 between the. cutters and bearingsupporting pins, and: of: retaining them in place is specifically described in the above-mentioned Patent No. 2,545,036.

The cutter supporting members 36 and cutters 61 mounted thereon, tend to occupy a retractedposition substantially and entirely within the confines of the main body 13 0f the bit. These cutter supporting members and cutters are expandible outwardly, to enlarge the sides of the well bore andto operate upon a formation shoulder C that the cutters produce in the latter. To accomplish the expansion, each cutter. supporting member 36. has an inclined expander surface 64.,onits inner portion below the hinge pin 38, which tapers in a downward and inward direction. Each expander surface terminates in a lock surface 65 formed on the cutter supporting member. Theoutward expansion is accomplished by producing relative longitudinal movement between the mandrel 10 and the bit body 13, which will produce correspondingly relative longitudinal movement between the cutter supporting members 36 and a tubular member 66 of the mandrel. This tubular mandrel includes a lower portion 67 slidable within a guide bushing 68 secured in a guide support 69 attached to the body and extending across the slotted region of the latter below the lock surfaces 65.

Located initially above the guide 69 and below the hinge pins 38, and in cutter supporting member recesses 70, is a mandrel lock and expander 71 having its outer surface 72 adapted to engage the expander surfaces 64 and the lock surfaces 65. The lock and expander 71 may be formed integrally with the tubular member 66, the upper end of the latter being piloted within a socket 73 in the lower portion of the kelly 12. An enlarged boss 74 on the tubular member engages a downwardly facing shoulder 75 on the kelly, the tubular member being held against this shoulder by a suitable split retainer ring 76 snapped into an internal groove 77 encompassing the Kelly socket 73 and engaging a downwardly directed shoulder 78 formed on the tubular member boss. Leakage between the boss 74 and the wall of the Kelly socket 73 is prevented by a suitable side seal, in the form of arubber O ring 79 disposed within a groove 80 in theboss'and engaging the wall of the socket.

The kelly 12 has. a central fluid passage 81 therethrough communicating with thestring of drill pipe B. Fluid pumped through this passage can pass into an aligned central passage 82 infthe tubular member 66, whereby drilling mud, or similar drilling fluid, can be pumped down through the tooljfor the purpose of removing the cuttings from tl1e well boreand flushing them up around the drill pipe to-the top of'the'hole;

As disclosed,--a central nozzle 83 is located in-the lower end portion of the tubular member passage 82. When the mandrel is in its lower positionwith respect to the body 13, this central nozzle will be located above a central enlarged cavity or body space 84 immediately below the body slots 37. This relatively large diameter space or passage 84 has a relatively small diameter central passage 85 leading downwardly from it to form an upwardly facing shoulder 86. The small diameter passage, in turn, opens into another relatively large diameter central passage 87 in the body terminating at the lower end of the body 13.

After the cutters 61 have been expanded outwardly, fluid discharged in a downward direction from the nozzle 83 will strike fluid in the upper enlarged passage 84, which is relatively dead fluid since it cannot readily pass downwardly through the restricted passage 85, the fluid discharged from the nozzle being deflected by this relatively dead fluid in lateral outward directions toward the cutters 61 to clean the cuttings from the region of the shoulder C and flush them upwardly around the tool A and the drill pipe B to the top of the well bore.

Assuming that the body 13 of the tool is elevated relatively along the tubular mandrel 10, the inclined expander surfaces 64 of the cutter supporting members will be shifted upwardly along the lock and expander portion 71 of the tubular member 66. During such upward shift ing, the cutter supporting members 36 and the cutters 61 carried thereby will be pivoted about the hinge pins 38 and urged in an outward direction. Movement of the body 13 with respect to the tubular mandrel 10 can continue until the cutters 61 have been shifted outwardly to their fullest extent, as determined by engagement of stop shoulders 88 on the cutter supporting members 36 with companion shoulders 89 formed in the body on opposite sides of the body slots 37. When such engagement occurs, the lower end 16 of the kelly portion of the tubular mandrel 10 will engage the body shoulder 17 and the lock and expander 71 on the tubular member 66 will be disposed behind-and in engagement with the lock surfaces 65 on the cutter supporting members 36.

It is to be noted that the lock surfaces 65 on the cutter supporting members 36 and the companion surfaces 72 on the lock and expander portion 71 of the tubular member 66 are substantially parallel to the axis of the drill bit, to prevent the reactive forces of the formation on the cutters 61 from moving the latter inwardly. As a practical matter, it is preferred that the coengaging lock surfaces 65,72'be inclined slightly in a downward direction toward the axis of the tool to insure release of the lock and expander portion 71 from the cutter supporting members 36 when the latter and the cutters 61 are to be shifted back to' their retracted positions.

The relative longitudinal movement between the tubu lar mandrel 10 and the body 13 of the tool, for effecting outward expansion of the cutters 61, is accomplished hydraulically. The counterbore 19 receiving the piston 18 of the drill stem member '12 is formed in the upper portion of the body 13, to provide the cylinder 21 having a cylinder wall 90 extending from a lower shoulder 91 defining the bottom of the counterbore to the loca tion of the upper guide member 26. As was previously described, this upper guide member 26 closes the upper end of the body 13, and can also prevent foreign substances from moving down into the body through the use of a suitable wiper ring 92, which may be in the form of a rubber, or rubber-like O ring, disposed in an internal groove 93 in the upper guide and slidably and sealingly engaging the periphery of the mandrel 1d.

The cylinder head 20 retained in the upper portion of the body or cylinder 21 has an inner seal ring 94, in the form of a rubber, or rubber-like, O ring, received within an internal groove 95 in the cylinder head and slidably and sealingly engaging the periphery of the {mandrel 10.. This head 20-also has an external sealing structure in the form of a rubber, or rubber-like, 6 ring" 96 disposed in an external groove 97 in the head and sealingly engaging the wall of the counterbore or cylinder 21. The head 20 itself has a depending skirt 98 that is engaged by the upper end of the piston portion 18 of the mandrel, for the purpose of limiting the extent of relative upward movement of the mandrel 16 with respect to the body 13 of the tool. This skirt 98 is disposed at the outer portion of the cylinder head 20, to provide an annular space 99 between the periphery of the mandrel or kelly 12 above the piston portion 18 and the skirt 98 itself, into which fluid under pressure from the central passage 81 of the mandrel can enter, such fluid flowing through intercommunicating lateral ports 100 in the mandrel immediately above the piston portion 18.

Fluid from the cylinder space 99 is prevented from passing downwardly around the periphery of the piston 18 by a suitable side seal ring 101, such as a rubber, or rubber-like, 0 ring, disposed in a piston groove 102 and sealingly engaging the cylinder Wall 90.

Fluid under pressure in the string of drill pipe B and within the tubular mandrel 10 is fed into the cylinder space 99 through the side ports 100, such fluid under pressure being developed by the back pressure built up through the necessity of the fluid to pass through the relatively restricted passage 82 through the tubular member 66 and the nozzle 83 at its lower portion. This back pressure imposed on the fluid in the cylinder space 99 acts in an upward direction on the cylinder head 28, urging the body 13 of the tool upwardly with respect to the tubular mandrel 10, and correspondingly elevating the cutter supporting members 36 and cutters 61 with respect to the lock and expander portion 71 of the tubular member 66, until the cutters 61 are expanded to their fullest extent. With the fluid pressure elevating the body relative to the mandrel, the tool can be rotated, the cutters 61 operating upon the formation and gradually being expanded outwardly as the body continues to be elevated along the mandrel until the cutters have been expanded outwardly to their fullest extent, as determined by engagement of the cutter supporting arm shoulders 88 with the companion body shoulders 89. When this occurs, the mandrel lock portion 71 is disposed behind the companion lock surfaces 65 of the cutter supporting members 36 to retain the cutters 61 in their outwardly expanded position, the downward drilling weight being transmitted from the lower end 16 of the kelly 12 to the body shoulder 17, and from the stop shoulders 89 on the latter on opposite sides of the slots 37 to the cutter supporting members 36, being transmitted from the latter through the cutters 61 to the formation shoulder C. The cutters 61 will remain locked in their outwardly expanded position, so long as drilling weight is being imposed upon the drill pipe B and the drill bit A, the cutters 61 operating upon the formation shoulder C to progressively enlarge the bore in a downward direction.

In the event the drill pipe B and drill bit A are elevated in the well bore, and in the absence of hydraulic pressure within the tool, the body 13 would tend to drop down along the mandrel 16, allowing the cutters 61 to return to their retracted position. If this were to occur, it would be necessary to first apply pressure to the tool to reexpand the cutters 61 before lowering the apparatus back to the position in which the cutters engage the shoulder C.

The apparatus disclosed in the drawings prevents the cutters 61 from inadvertently retracting from their maximum outwardly expanded position in the absence of fluid pressure within the drill pipe B and the mandrel passages 81, 82, and upon elevation of the tool to raise the cutters above the shoulder. To accomplish this. purpose, a detent device is provided between the body 13 and the mandrel 10 to retain the body in its elevated position relative to the mandrel in which the cutters are expanded outwardly. However, the mandrel and body can be released from one another, to allowlthe body to be lowered relative to the mandreh enabling the cutters to return to their retracted position. When in this lower position, the body and mandrel are again releasably locked to each other to prevent inadvertent outward expansion of the cutters.

As specifically shown, one or more detents are provided between the mandrel and the body 13 of the tool. Each detent includes a ball movable radially in a radial passage 102 formed through the mandrelat a particular distance above the mandrel ports 100. The inner portion 103 of the ball detent passage is smaller in diameter than its outer portion to form a shoulder 104 against which a helical compression spring 105 can seat, the outer end of this spring engaging the ball 101 and urging it in a direction radially outwardly of' the mandrel 10. When the body 13 is in its lowermost position relative to the mandrel, such as shown in Fig. 1, the balls 101 are disposed opposite an internal circumferential groove 106 formed in the cylinder head 20 immediately below its upper internal seal ring 94. This groove 106 is of such depth that the detent ball 101 can partially enter it, and is of such a length that the mandrel 10 and body 13 can move only a relatively short distance with respect to each other before further movement is precluded by engagement of the ball 101 with the upper or lower ends of the groove 106.

Thus, the balls 101 will be disposed partly within the radial passages 102 and partly within the circumferential grooves 106, to releasably lock the body 13 and mandrel 10 in their initial position, wherein the cutters 61 are retracted. However, the center of each ball 101 is still disposed inwardly of the periphery of the mandrel 10, wherein an upward force imposed on the body will cause the lower side of the groove 106 to engage each ball and shift it inwardly in the passage 102 against the compressive force of the spring 105, until all of the balls are disposed completely within the confines of theradial passages 102, whereupon the body 13 can move upwardly with respect to the mandrel 10, the balls merely sliding along the inner surface of the cylinder head 20' below the internal groove 106.

When the cutters 61 have been expanded outwardly to their fullest extent, and the lock portion 71 of the tubular member 66 is disposed behind the companion lock surfaces 65 on the cutter supportingmembers 36, the detent passages 102 are then disposed immediately below a downwardly facing shoulder 107 of the cylinder head 20 at the upper end of the head skirt 98. The springs 105 can urge the balls 101 outwardly, so that they engage such shoulder 107. The tool is rotated and the hole enlarging operation proceeds, with the fluid being pumped down through the apparatus. The fluid pressure is constantly tending to elevate and retain the body 13 in an elevated position relative to the mandrel 10, but the upward movement is obviously limited by engagement of the body shoulder 17 with the lower end 16 of the kelly 12. In the event the tool is elevated in the enlarged well bore to raise the cutters 61 above the shoulder C, and if the pumping of fluid through the tool is discontinued, the absence of hydraulic pressure in the cylinder 21 will not cause the weight of the body and the cutter members mounted thereon to drop the body and cutters with respect to the mandrel 10, which would allow the cutters to retract. The springs 105 exert suflicient force on the ball deten-ts 101 to retain them under the cylinder head shoulder 107 and prevent such action from occurring. As a matter of fact, it is only when the tool A has been elevated in the well bore to the point at which the cutter supporting members 36 enter a smaller diameter portion of the well bore, or engage the shoe of the well casing, that sufficient restraint to upward movement of the body13 occurs, permitting an upward force to be imposed on the mandrel to cause the shoulder 107 to push the balls 101 back into their confining bores 102. The mandrel 10 can now be moved upwardly of the body 13, with the, balls 101 sliding along the inner wall of the head 20 until the balls again snap out into the internal groove106, to releasably retain the body 13 and mandrel 10.in.a relative cutter'releasing position. The apparatus can now be elevated through the well casing to the top of the hole.

It is preferred that the radial passages 102 containing the balls 101 establish communication between the central Kelly passage 81 and the exterior of the mandrel kelly 12. Despite such communication, the pumping of fluid through the apparatus will not provide any leakage offluid from the cylinder space 99 since the same pressure is being imparted to the fluid in the upper passages or ports 102 as in the lower passages or ports 100, the disposition of the upper head seal ring 94 above the detent passages or ports 102, preventing fluid from leaking out of the cylinder space in such direction. However, the upper ports 102 facilitate the removal of fluid from the cylinder space 99 when the mandrel 10 is to be elevated with respect to the body 13 to secure retraction of the cutters 61 from their outwardly expanded position. Thus, upward movement of the mandrel might ordinarily be accompanied by fluid being forced out of the cylinder space 99 back through the lower ports 100 into the central passage 81 in the mandrel. However, in the event that such return flow of fluid is prevented or retarded, as through the existence of some sand in the lower portion of the cylinder space resting upon the piston 18, then the fluid can be forced around the periphery of the balls 101 and radially inwardly through the upper ports 102 into the mandrel passage 81.

It is preferred that the balls 101 make a sliding fit with the walls of'the lateral passages 102. This will permit fluid to pass around the balls 101, but solid particles, such as sand and the like, are prevented from passing thereby. During the use of the tool, the relatively close fit of the halls 101 in the passages 102 will prevent any sand in the drilling fluid from passing through the upper ports 102 and around the balls into the cylinder space 99, which might tend to clog the latter. The chance of sand entering through the lower ports 100 and rising upwardly in the cylinder space 99 is relatively small. However, any sand that might enter the cylinder space through the lower ports and tending to plug the latter will not prevent retraction of the apparatus, since the elevation of the mandrel 10 relative to the body 13, as explained above, will force some of the liquid in the cylinder space back around the balls 101, through the upper set of ports 102, and into the central passage 81.

The lower portion of the apparatus disclosed in the drawings is formed as a pilot cutter device or guide, to assist in retaining the apparatus in a central position Within a previously drilled hole. The lower portion of the body 13 is provided with longitudinal, circumferentially spaced grooves 108, each of which terminates at a downwardly facing transverse body shoulder 109a, and which opens downwardly through the lower end of the body. Each groove 108 includes a relatively wide inner portion 109 communicating with the periphery of the body through a substantially narrower central portion 110 to form opposed longitudinal body ribs 111. A cutter and pilot blade 112 is insertable upwardly into. each groove 108, each blade including longitudinally extending transverse flanges 113 adapted to slide upwardly within the inner groove portion 109 and having longitudinal grooves 114m its medial portion to receive the body ribs 111, the outer portion of each cutter blade 112 projecting laterally from the body 13 to the hole in which the tool is to operate.

The upper outer end 115 of each blade 11?. is inclined in an upward and inward direction, to prevent the blades from hanging up on projections. or casing coupling spaces. The lower portion 116 of each blade; iscurved' in a downward and inward direction to. forms a guide, such curved portions merging into a bottom hole engaging portion 117, which extends inwardly across the bottom of the body. As stated above, the blade 112 is inserted in the body 13 until its upper end engages the body shoulder 109a, at which time a tapered inner surface 118 on each blade will engage a companion tapered surface 119 at the lower end of the body.

Once the blades 112 are moved upwardly into the body grooves 108 into engagement with the body shoulder 109a, they are each retained in such position by a holding screw 120. This holding screw has a threaded shank 121 received within a lateral threaded bore 122 in the body, the head 123 of the screw being slidable within an enlarged diameter bore portion 124 disposed inwardly of the longitudinal body groove 168. Before a cutter blade 112 is moved upwardly into the body 13, the screw 120 is threaded inwardly of the lateral bore 122 to its fullest extent, in which the outer end of the head 123 is disposed laterally inward of the longitudinal groove 1G8, so as not to interfere with upward sliding of the blade 112 within the body groove. When the blade is disposed in engagement with the body shoulder 109a, a suitable tool, such as a screw driver (not shown), is inserted through a late .1 hole 125 in the body in alignment with a non-cir i:-.-.1 opening 126 in the screw head, the screw 120 being rotated in an unthreading direction, so that it is fed laterally outward to locate its head 123 in a transverse groove 127 formed in the inner portion of the cutter blade 112. The longitudinal extent of the groove 127 is only slightly greater than the diameter of the head, to prevent the blade from having any substantial motion lengthwise of the body. If desired, to prevent inadvertent return threading of the screw 129 into the lateral bore 122, a helical spring 128 may be located in the enlarged bore portion 124, bearing against the shoulder 130 at the inner end of the enlarged bore and against the head 123 of the screw. However, the spring 123 need not be used if desired.

In the use of the pilot arrangement, downward forces on the pilot blades 112 are transmitted directly from the body shoulders 109a to the blades, whereas rotary motion is transmitted from the body 13 directly to the blades 112, such rotary motion not being transferred at all through the retaining screws 120. The blades 112 are preferably hardfaced, to increase their life.

The inventor claims:

1. In a rotary well drilling bit connectible to a tubular drill string: a main body having a fluid passage therein adapted to communicate with the tubular drill string; cutter means mounted on said body for expansion laterally of said body; hydraulically operable means operatively connected to said cutter means for expanding said cutter means laterally outward; an inlet for conducting fluid under pressure from said passage to said hydraulically operable means to actuate said hydraulically operable means and cause said hydraulically operable means to expand said cutter means laterally outward; an outlet for conducting fluid from said hydraulically operable means to said passage; and releasable holding means in said outlet engageable with said hydraulically operable means to releasably hold said cutter means expanded laterally outward.

2. In a rotary well drilling bit connectible to a tubular drill string: a main body having a fluid passage therein adapted to communicate with the tubular drill string; cutter means mounted on said body for expansion laterally of said body; hydraulically operable means operatively connected to said cutter means for expanding said cutter means laterally outward; passage means for conducting fluid between said passage and hydraulically operable means, whereby said fluid acts on said hydraulically operable means to cause said hydraulically operable means to expand said cutter means laterally outward; and releasable holding means in said passage means engageable with said hydraulically operable means to releasably hold said cutter means expanded laterally outward.

3. In a rotary well drilling bit connectible to a tubular drill string: a main body having a fluid passage therein adapted to communicate with the tubular drill string; cutter means mounted on said body for expansion laterally of said body; hydraulically operable means operatively connected to said cutter means for expanding said cutter means laterally outward; passage means for conducting fluid between said passage and hydraulically operable means, whereby said fluid acts on said hydraulically operable means to cause said hydraulically operable means to expand said cutter means laterally outward; and releasable holding means in said passage means engageable with one portion of said hydraulically operable means to releasably hold said cutter means expanded laterally outward, said holding means being releasably engageable with another portion of said hydraulically operable means when said cutter means is in retracted position on said body to releasably hold said cutter means in such retracted position.

4. In a rotary well drilling bit connectible to a tubular drill string: a main body having a fluid passage therein adapted to communicate with the tubular drill string; cutter means mounted on said body for expansion laterally of said body; hydraulically operable means operatively connected to said cutter means; an inlet for conducting fluid under pressure from said passage to said hydraulically operable means to actuate said hydraulically operable means and expand said cutter means laterally outward; an outlet for conducting fluid from said hydraulic-ally operable means to said passage; a detent element in said outlet engageable with said hydraulically operable means to releasably hold said cutter means expanded laterally outward; and a spring in said outlet engaging said element to urge it into engagement with said hydraulically operable means.

5. In a rotary well drilling bit connectible to a tubular drill string: a main body having a fluid passage therein adapted to communicate with the tubular drill string; cutter means mounted on said body for expansion laterally of said body; hydraulically operable means operatively connected to said cutter means; passage means for conducting fluid between said passage and hydraulically operable, means; a detent element in said passage means engageable with said hydraulically operable means to releasably hold said cutter means expanded laterally outward; and a spring insaid passage means engaging said element to urge it into engagement with said hydraulically operable means.

6. In a rotary well drilling bit connectible to a tubular drill string: a main body having a fluid passage therein adapted to communicate with the tubular drill string; cutter means mounted on said body for expansion laterally of said body; hydraulically operable means operatively connected to said cutter means; passage means for conducting fluid between said passage and hydraulically operable means; a detent element in said passage means engageable with one portion of said hydraulically operable means to releasably hold said cutter means expanded laterally outward; said detent element being releasably engageable with another portion of said hydraulically operable means when said cutter means is in retracted position on said body.

7. In a rotary well drilling bit connectible to a tubular drill string: a main body having a fluid passage therein adapted to communicate with the tubular drill string; cutter means mounted on said body for expansion laterally of said body; hydraulically operable means operatively connected to said cutter means; an inlet for conducting fluid under pressure from said passage to said hydraulically operable means to actuate said hydraulically operable means and expand said cutter means laterally outward; an outlet for conducting fluid from said hydraulically operable means to said passage; a detent element in said outlet engageable with said hydraulically operable means to releasably hold said cutter means expanded laterally outward; and a spring in said outlet engaging said element to urge it into engagement with said hydraulically operable means; the diameters of said detent element and outlet being substantially equal.

8. In a rotary well drilling bit connectible to a tubular drill string: a main body having a fluid passage therein adapted to communicate with the tubular drill string; cutter means mounted on said body for expansion laterally of said body; hydraulically operable means operatively connected to said cutter means; passage means for conducting fluid between said passage and hydraulically operable means; a detent element in said passage means engageable with said hydraulically operable means to releasably hold said cutter means expanded laterally outward; and a spring in saidpassage means engaging said element to urge it into engagement with said hydraulically operable means, the diameters of said detent element and passage means being substantially equal,

9. In a rotary well drilling bit connectible to a tubular drill string: a main body; cutter means mounted on said body for expansion laterally ofsaid body; a mandrel connectible to a drill string and slidably splined to said body; said mandrel having afluid passage communicating with the drill string; coengageable expander means on said mandrel and cutter means; hydraulically operable means on and operatively connected to said body; means for feeding fluid under pressure from said passage into said hydraulically operable means to cause said hydraulically operable means to elevate said body and cutter means with respect to said mandrel to cause said expander means to expand said cutter means laterally outward; and releasable holding means on said mandrel andhydraulically operable means to releasably hold said cutter means expanded laterally outward.

10. In a rotary well drilling bit connectible to a tubular drill string: a main body; cutter means. mounted; on said body for expansion laterally of said body; a mandrel connectible toa drill string and slidably splined to said body; said mandrel having afluid passage communicating with the drill string; coengageableexpander means ongsaid mandrel and cutter means; hydraulically operable means on said body; means for feeding fluid under pressure from said passage into said hydraulically operable means to elevate said body and cutter means with respect to. said mandrel to cause said expander means to expand said cutter means laterally outward; an. outlet in said mandrel for conducting fluid from said hydraulically operable means to said passage; and releasable holding means: in said outlet releasably engaging said hydraulically operable meansto releasably hold said cutter means expanded laterally outward. i

11. In a rotary well drilling bit connectible to a tubular drill string: a main body; cutter means mounted on said body for expansion laterally of said, body; a mandrel connectible to a drill string and slidably splined to said body; said mandrel having a fluid passage communicating with the drill string; coengageable expander means on said mandrel and cutter. means; hydraulically operable means. on and operatively connected to said body; means for feeding fluid under pressure from said passage into said hydraulically operable means to cause said hydraulically operable means to elevate said body and cutter means, with respect to said mandrel to cause said 'expander means to expand said cutter means laterally outward; and releasable holding means in saidfeeding means releasably engaging said hydraulically operable means to releasably hold said cutter ineans expanded laterally outward.

12. In a rotary well drilling bit connectible to atubular drill string: a main body; cutter means mounted on said body forv expansion laterally of said body; a mandrel connectible to a drill string and slidably splined to said body; said mandrel "having .a'fluid passage communicating with the drill string; coengageable expander means on said mandrel. and cutter means; hydraulically operable means on said body; means for feeding fluid under pressure from said passage into said hydraulically operable means to elevate said-body and cutter means-with respect to said mandrel to cause said expander means to. expand said cutter means laterally outward; a detent element in said feeding means engageable with said hydraulically operable means to releasably hold said cutter means expanded laterallyoutward; and a spring in said feeding means engaging said element to urge it into engagement with said hydraulically operable means.

13. In a rotary well drilling bit connectible to a tubular drill string: a main body; cutter means mounted on said body for expansion laterally of said body; a mandrel connectible to a drill string and slidably splined to said body; said mandrel having a fluid passage communicating with the drill string; coengageable expander means on said mandrel and cutter means; hydraulically operable means on saidbody; means for feeding fluid under pressure from said passage into said hydraulically operable means to elevate said body and cutter means with respect to said mandrel to cause said expander means to expand said cutter means laterally outward; an outlet in said mandrel for conducting fluid from said hydraulically operable means to said passage; a detent element in said outlet engageable with said hydraulically operable means to releasably hold said cutter means expanded laterally outward; and a spring in said outlet engaging said element to urge it into engagement with said hydraulically operable means.

14. In a rotary well drilling bitconnectible to a tubular drill string: a main body; cutter means mounted on said body for expansion laterally of said body; a mandrel connectible to a drill string and slidably splined to said body; said mandrel having a fluid passage communicating with the drill string; coengageable expander, means on said mandrel and cutter means; hydraulically operable means on saidbodygmeans for feeding fluid under pressure from said passage into said hydraulically operable means to elevate said body and cutter means with respect to said mandrel to cause said expander means to expand said cutter means laterally outward; an outlet in saidmandrcl for conducting fluid from said hydraulically operable means to said passage; a detent element in saidoutlet engageable with one portion of said hydraulically operable means to releasably hold said cutter. means expanded laterally outward; said detent element being releasably engageable with another portion of said hydraulically operable means when said cutter means is in retracted position on said body; and a spring in said outlet engaging said element to urge it into engagement with said hydraulically operable means.

15. In a rotary well drilling bit connectible to a tubular drill string: a main body; cutter means mounted on said body for expansion laterally of said body; a mandrel connectible to a drill string and slidably splined to said body; said mandrel having a,fluid passage communicating with the drill string; coengageable expander means on said mandrel and. cutter means; hydraulically operable means on andoperatively connectedlto said body; means.

for feeding fluid under pressurefrom said passage into said hydraulically operable means to cause said hydraulically operable means to. elevatev saidtbody and cutter means with respect to said mandrel tocause, said expander means to expand said cutter means laterally outward; and, releasable holding means in said feeding means releasably engaging said. hydraulically operable means to releasably hold said cutter means in retracted position on said body.

References Cited in the file of this patent UNITED STATES PATENTS 1,478,306 Sweetman Dec. 18, 192-3. 2,545,035 Kammerer- Mar. 13, 1951- 2,755,070 Kammerer July 17, 1956 

